"You'll need a new app to open this file" is probably the most common error faced by millions of Windows users every day. This is either because the program required to open a file is not available on your system or there may be other issues.

What is .RCO file extension?

File used by the PlayStation Portable (PSP), a gaming device developed by Sony; contains resources for the PSP, including system information, sounds, icons, and other theme graphics; commonly used to customize the look and feel of the PSP interface.
One commonly edited RCO file is topmenu_plugin.rco, which contains the main menu and submenu XMB icons and text. RCO files are located in the flash0:/vsh/resource directory on a PSP flash card.
You can see a list of software programs here on easyfileopener.org that can open this file type so that you don’t need to search for it on the web. You can then open your file with this extension using a software listed below.